From Ancient and Medieval Philosophy: Essential Selections, by James Fieser


Copyright 2016, updated 12/1/2016




Life of Thomas Aquinas

Faith and Reason

Proofs for God

Divine Attributes and Names

The Forms and Sensory Perception

Divine Providence

Natural Law


LIFE OF THOMAS AQUINAS (1225–1274) (Stockl, Handbook)


Thomas Aquinas was born at Kocca Sicca, near Monte Cassino, in 1225. He was a younger son of a Count Landolf of Aquino, who was related to the family of the Hohenstauffen Emperors. He received his education at Monte Cassino and Naples. Overcoming the opposition of his parents and family, he joined the Dominican Order at Naples. He continued his studies at Cologne and Paris, under the guidance of Albertus Magnus, and, after completing them, he filled the professorial chair at Cologne, Paris, Bologna, and Naples. He lectured on philosophy and theology, and his renown soon eclipsed that of his master. Crowds of youthful students came from every country in Christendom to hear from his mouth the teachings of wisdom. Finally, he was summoned from Naples by Gregory X to attend the Council of Lyons, but died on the way, at the Abbey of Fossa Nuova, in the year 1274. He was canonized in 1323 by Pope John XXII., and is known to scholastic philosophers as the " Doctor Angelicus."




Two Main Points of Faith: The Trinity and the Incarnation (CT 1.2)

Faith is a certain foretaste of that knowledge which is to make us happy in the life to come. The Apostle says, in Hebrews 11:1, that faith is “the substance of things to be hoped for,” as though implying that faith is already, in some preliminary way, inaugurating in us the things that are to be hoped for, that is, future beatitude. Our Lord has taught us that this beatific knowledge has to do with two truths, namely, the divinity of the Blessed Trinity and the humanity of Christ. That is why, addressing the Father, He says: “This is eternal life: that they may know You, the only true God, and Jesus Christ, whom You sent” (John 17:3). All the knowledge imparted by faith hinges on these two points, the divinity of the Trinity and the humanity of Christ. This should give us no surprise: the humanity of Christ is the way by which we come to the divinity. Therefore, while we are still wayfarers, we ought to know the road leading to our goal. In the heavenly fatherland adequate thanks would not be given to God if men had no knowledge of the way by which they are saved. This is the meaning of our Lord’s words to His disciples: “And where I go you know, and the way you know” (John 14:4).


Twofold Division of Divine Truths: Those Attainable through Reason, Those Not (SCG 1.3)

Because not every truth allows for the same manner of manifestation, and "a well-educated man will expect exactness in every class of subject, according as the nature of the thing admits," as is very well remarked by the Philosopher (Eth. Nicom. I, 1094b), we must first show what manner of proof is possible for the truth that we have now before us. The truths that we confess concerning God are twofold. Some things true of God are beyond all the competence of human reason, as that God is Three and One. Other things there are to which even human reason can attain, as the existence and unity of God, which philosophers have proved to a demonstration under the guidance of the light of natural reason. However, it most clearly appears that there are points of absolute intelligibility in God altogether beyond the compass of human reason. For since the leading principle of all knowledge of any given subject-matter is an understanding of the thing's innermost being, or substance (according to the doctrine of the Philosopher, that the essence is the principle of demonstration) it follows that the manner of our knowledge of the substance must be the manner of knowledge of whatever we know about the substance. Hence if the human understanding comprehends the substance of anything, as of a stone or triangle, none of the points of intelligibility about that thing will exceed the capacity of human reason. But this is not our case with regard to God. The human understanding cannot go so far through its natural power as to grasp His substance, since under the conditions of the present life the knowledge of our understanding begins with sense. Therefore, objects beyond sense cannot be grasped by human understanding except so far as knowledge is gathered of them through the senses. But things of sense cannot lead our understanding to read in them the essence of the Divine Substance, inasmuch as they are effects inadequate to the power that caused them. Nevertheless our understanding is thereby led to some knowledge of God, namely, of His existence and of other attributes that must necessarily be attributed to the First Cause. There are, therefore, some points of intelligibility in God, accessible to human reason, and other points that altogether transcend the power of human reason.

            The same thing may be understood from consideration of degrees of intelligibility. Of two minds, one of which has a keener insight into truth than the other, the higher mind understands much that the other cannot grasp at all. This is clear in the plain man (in rustico), who can in no way grasp the subtle theories of philosophy. Now the intellect of an angel excels that of a man more than the intellect of the ablest philosopher excels that of the plainest of plain men (rudissimi idiotae). The angel has a higher standpoint in creation than man as a basis of his knowledge of God. For, the substance of the angel, by which he is led to know God by a process of natural knowledge, is nobler and more excellent than the things of sense, and even than the soul itself, by which the human mind rises to the knowledge of God. But the Divine Mind exceeds the angelic much more than the angelic the human. For the Divine Mind of its own comprehensiveness covers the whole extent of its substance, and therefore perfectly understands its own essence, and knows all that is knowable about itself. But an angel of his natural knowledge does not know the essence of God, because the angel's own substance, by which it is led to a knowledge of God, is an effect that is inadequate to the power of the cause that created it. Hence not all things that God understands in Himself can be grasped by the natural knowledge of an angel; nor is human reason competent to take in all that an angel understands of his own natural ability. Thus, it would be the height of madness in a plain man to declare a philosopher's propositions false, because he could not understand them. So too and much more would a man show great foolishness if he suspected of falsehood a divine revelation given by the ministry of angels, on the mere ground that it was beyond the investigation of reason.

            The same thing clearly appears from the incapacity which we daily experience in the observation of nature. We are ignorant of many properties of the things of sense; and of the properties that our senses do apprehend, in most cases we cannot perfectly discover the reason. Much more is it beyond the competence of human reason to investigate all the points of intelligibility in that supreme excellent and transcendent substance of God. Consistent with this is the saying of the Philosopher, that "as the eyes of bats are to the light of the sun, so is the intelligence of our soul to the things most clear by nature" (Aristotle, Metaphysics I, min. l).

            To this truth Holy Scripture also bears testimony. For it is said: “Perhaps you will seize upon the traces of God, and fully discover the Almighty” (Job 11:7). And, “Indeed, God is great, and surpassing our knowledge” (Job 36:26). And, “We know in part” (I Cor. xiii, 9). Not everything, therefore, that is said of God, even though it is beyond the power of reason to investigate, is at once to be rejected as false.


Whether, besides Philosophy, any Further Doctrine Is Required? (ST 1.1.1)

            Objection 1: It seems that, besides philosophical science, we have no need of any further knowledge. For man should not seek to know what is above reason: "Do not seek the things that are too high for you" (Ecclus. 3:22). But whatever is not above reason is fully treated of in philosophical science. Therefore any other knowledge besides philosophical science is superfluous.

            Obj. 2: Further, knowledge can be concerned only with being, for nothing can be known, except what is true; and all that is, is true. But everything that is, is treated of in philosophical science—even God Himself; so that there is a part of philosophy called theology, or the divine science, as Aristotle has proved (Metaph. vi). Therefore, besides philosophical science, there is no need of any further knowledge.

            On the contrary, It is written (2 Tim. 3:16): "All Scripture inspired of God is profitable to teach, to reprimand, to correct, to instruct in justice." Now Scripture, inspired of God, is no part of philosophical science, which has been established by human reason. Therefore it is useful that besides philosophical science, there should be other knowledge, i.e., inspired of God.

            I answer that, It was necessary for man's salvation that there should be a knowledge revealed by God besides philosophical science established by human reason. Firstly, indeed, because man is directed to God, as to an end that surpasses the grasp of his reason: "The eye has not seen, besides you, God, what things you have prepared for them that wait for your" (Isa. 66:4). But the end must first be known by men who are to direct their thoughts and actions to the end. Hence it was necessary for the salvation of man that certain truths which exceed human reason should be made known to him by divine revelation. Even concerning those truths about God which human reason could have discovered, it was necessary that man should be taught by a divine revelation. For the truth about God that reason could discover would only be known by a few, and after a long time, and with the addition of many errors. However, man's whole salvation, which is in God, depends upon the knowledge of this truth. Therefore, in order that the salvation of men might be brought about more properly and more surely, it was necessary that they should be taught divine truths by divine revelation. It was therefore necessary that besides philosophical science established by reason, there should be a sacred science learned through revelation.

            Reply Obj. 1: Although those things which are beyond man's knowledge may not be sought for by man through his reason, nevertheless, once they are revealed by God, they must be accepted by faith. Hence the sacred text continues, "For many things are shown to thee above the understanding of man" (Ecclus. 3:25). In this, the sacred science consists.

            Reply Obj. 2: Sciences are differentiated according to the various means through which knowledge is obtained. For the astronomer and the physicist both may prove the same conclusion: that the earth, for instance, is round: the astronomer by means of mathematics (i.e., abstracting from matter), but the physicist by means of matter itself. Hence there is no reason why those things which may be learned from philosophical science, so far as they can be known by natural reason, may not also be taught us by another science so far as they fall within revelation. Hence theology included in sacred doctrine differs in kind from that theology which is part of philosophy.




Whether the Existence of God Is Self-Evident? (ST 1.2.1)

            Objection 1: It seems that the existence of God is self-evident. Now those things are said to be self-evident to us the knowledge of which is naturally implanted in us, as we can see in regard to first principles. But as Damascene says (De Fide Orth. i, 1,3), "the knowledge of God is naturally implanted in all." Therefore the existence of God is self-evident.

            Obj. 2: Further, those things are said to be self-evident which are known as soon as the terms are known, which the Philosopher (1 Poster. iii) says is true of the first principles of demonstration. Thus, when the nature of a whole and of a part is known, it is at once recognized that every whole is greater than its part. But as soon as the signification of the word "God" is understood, it is at once seen that God exists. For by this word is signified that thing than which nothing greater can be conceived. But that which exists actually and mentally is greater than that which exists only mentally. Therefore, since as soon as the word "God" is understood it exists mentally, it also follows that it exists actually. Therefore the proposition "God exists" is self-evident.

            Obj. 3: Further, the existence of truth is self-evident. For whoever denies the existence of truth grants that truth does not exist: and, if truth does not exist, then the proposition "Truth does not exist" is true: and if there is anything true, there must be truth. But God is truth itself: "I am the way, the truth, and the life" (John 14:6) Therefore "God exists" is self-evident.

            On the contrary, No one can mentally admit the opposite of what is self-evident; as the Philosopher (Metaph. iv, lect. vi) states concerning the first principles of demonstration. But the opposite of the proposition "God is" can be mentally admitted: "The fool said in his heart, There is no God" (Ps. 52:1). Therefore, that God exists is not self-evident.

            I answer that, A thing can be self-evident in either of two ways: on the one hand, self-evident in itself, though not to us; on the other, self-evident in itself, and to us. A proposition is self-evident because the predicate is included in the essence of the subject, as "Man is an animal," for animal is contained in the essence of man. If, therefore the essence of the predicate and subject be known to all, the proposition will be self-evident to all; as is clear with regard to the first principles of demonstration, the terms of which are common things that no one is ignorant of, such as being and non-being, whole and part, and such like. If, however, there are some to whom the essence of the predicate and subject is unknown, the proposition will be self-evident in itself, but not to those who do not know the meaning of the predicate and subject of the proposition. Therefore, it happens, as Boethius says (Hebdom., the title of which is: "Whether all that is, is good"), "that there are some mental concepts self-evident only to the learned, as that incorporeal substances are not in space." Therefore I say that this proposition, "God exists," of itself is self-evident, for the predicate is the same as the subject, because God is His own existence as will be hereafter shown (Q. 3, Art. 4). Now because we do not know the essence of God, the proposition is not self-evident to us; but needs to be demonstrated by things that are more known to us, though less known in their nature—namely, by effects.

            Reply Obj. 1: To know that God exists in a general and confused way is implanted in us by nature, inasmuch as God is man's beatitude. For man naturally desires happiness, and what is naturally desired by man must be naturally known to him. This, however, is not to know absolutely that God exists; just as to know that someone is approaching is not the same as to know that Peter is approaching, even though it is Peter who is approaching; for many there are who imagine that man's perfect good which is happiness, consists in riches, and others in pleasures, and others in something else.

            Reply Obj. 2: Perhaps not everyone who hears this word "God" understands it to signify something than which nothing greater can be thought, seeing that some have believed God to be a body. Yet, granted that everyone understands that by this word "God" is signified something than which nothing greater can be thought, nevertheless, it does not therefore follow that he understands that what the word signifies exists actually, but only that it exists mentally. Nor can it be argued that it actually exists, unless it be admitted that there actually exists something than which nothing greater can be thought; and this precisely is not admitted by those who hold that God does not exist.

            Reply Obj. 3: The existence of truth in general is self-evident but the existence of a Primal Truth is not self-evident to us.


Whether God Exists (The Five Ways) (ST 1.2.3)

            Objection 1: It seems that God does not exist; because if one of two contraries be infinite, the other would be altogether destroyed. But the word "God" means that He is infinite goodness. If, therefore, God existed, there would be no evil discoverable; but there is evil in the world. Therefore God does not exist.

            Obj. 2: Further, it is superfluous to suppose that what can be accounted for by a few principles has been produced by many. But it seems that everything we see in the world can be accounted for by other principles, supposing God did not exist. For all natural things can be reduced to one principle which is nature; and all voluntary things can be reduced to one principle which is human reason, or will. Therefore there is no need to suppose God's existence.

            On the contrary, It is said in the person of God: "I am Who am." (Ex. 3:14)

            I answer that, The existence of God can be proved in five ways.


Primary Mover Producing Motion in the World

            The first and more clear way is the argument from motion. It is certain, and evident to our senses, that in the world some things are in motion. Now whatever is in motion is put in motion by another, for nothing can be in motion unless it is in potentiality to that towards which it is in motion; whereas a thing moves inasmuch as it is in act. For motion is nothing else than the reduction of something from potentiality to actuality. But nothing can be reduced from potentiality to actuality, except by something in a state of actuality. Thus that which is actually hot, as fire, makes wood, which is potentially hot, to be actually hot, and thereby moves and changes it. Now it is not possible that the same thing should be at once in actuality and potentiality in the same respect, but only in different respects. For what is actually hot cannot simultaneously be potentially hot; but it is simultaneously potentially cold. It is therefore impossible that in the same respect and in the same way a thing should be both mover and moved, i.e. that it should move itself. Therefore, whatever is in motion must be put in motion by another. If that by which it is put in motion be itself put in motion, then this also must be put in motion by another, and that by another again. But this cannot go on to infinity, because then there would be no first mover, and, consequently, no other mover; seeing that subsequent movers move only inasmuch as they are put in motion by the first mover, just as the staff moves only because it is put in motion by the hand. Therefore it is necessary to arrive at a first mover, put in motion by no other; and this everyone understands to be God.


Primary Efficient Cause producing Order of Efficient Causes

            The second way is from the nature of the efficient cause. In the world of sense we find there is an order of efficient causes. There is no case known (neither is it, indeed, possible) in which a thing is found to be the efficient cause of itself; for then it would be prior to itself, which is impossible. Now in efficient causes it is not possible to go on to infinity, because in all efficient causes following in order, the first is the cause of the intermediate cause, and the intermediate is the cause of the ultimate cause, whether the intermediate cause be several, or only one. Now to take away the cause is to take away the effect. Therefore, if there is no first cause among efficient causes, there will be no ultimate, nor any intermediate cause. But if in efficient causes it is possible to go on to infinity, there will be no first efficient cause, neither will there be an ultimate effect, nor any intermediate efficient causes; all of which is plainly false. Therefore it is necessary to admit a first efficient cause, to which everyone gives the name of God.


Primary Necessary Being

            The third way is taken from possibility and necessity, and runs thus. We find in nature things that are possible to be and not to be, since they are found to be generated, and to corrupt, and consequently, they are possible to be and not to be. But it is impossible for these always to exist, for that which is possible not to be at some time is not. Therefore, if everything is possible not to be, then at one time there could have been nothing in existence. Now if this were true, even now there would be nothing in existence, because that which does not exist only begins to exist by something already existing. Therefore, if at one time nothing was in existence, it would have been impossible for anything to have begun to exist; and thus even now nothing would be in existence—which is absurd. Therefore, not all beings are merely possible, but there must exist something the existence of which is necessary. But every necessary thing either has its necessity caused by another, or not. Now it is impossible to go on to infinity in necessary things which have their necessity caused by another, as has been already proved in regard to efficient causes. Therefore we cannot but postulate the existence of some being having of itself its own necessity, and not receiving it from another, but rather causing in others their necessity. This all men speak of as God.


Maximally Perfect Being causing Lower Degrees of Perfection

            The fourth way is taken from the gradation to be found in things. Among beings there are some more and some less good, true, noble and the like. But “more” and “less” are predicated of different things, according as they resemble in their different ways something which is the maximum, as a thing is said to be hotter according as it more nearly resembles that which is hottest; so that there is something which is truest, something best, something noblest and, consequently, something which is uttermost being; for those things that are greatest in truth are greatest in being, as it is written in Metaphysics. ii. Now the maximum in any genus is the cause of all in that genus; as fire, which is the maximum heat, is the cause of all hot things. Therefore there must also be something which is to all beings the cause of their being, goodness, and every other perfection; and this we call God.


Intelligent Being moving Natural Things Towards and End

            The fifth way is taken from the governance of the world. We see that things which lack intelligence, such as natural bodies, act for an end, and this is evident from their acting always, or nearly always, in the same way, so as to obtain the best result. Hence it is plain that not fortuitously, but designedly, do they achieve their end. Now whatever lacks intelligence cannot move towards an end, unless it be directed by some being endowed with knowledge and intelligence; as the arrow is shot to its mark by the archer. Therefore some intelligent being exists by whom all natural things are directed to their end; and this being we call God.


            Reply Obj. 1: As Augustine says (Enchiridion xi): "Since God is the highest good, He would not allow any evil to exist in His works, unless His omnipotence and goodness were such as to bring good even out of evil." This is part of the infinite goodness of God, that He should allow evil to exist, and out of it produce good.

            Reply Obj. 2: Since nature works for a determinate end under the direction of a higher agent, whatever is done by nature must be traced back to God, as to its first cause. So also whatever is done voluntarily must also be traced back to some higher cause other than human reason or will, since these can change or fail; for all things that are changeable and capable of defect must be traced back to an immovable and self-necessary first principle, as was shown in the body of the Article.


Whether It Is an Article of Faith That the World Began? (ST 1.46.2)

            Objection 1: It would seem that it is not an article of faith but a demonstrable conclusion that the world began. For everything that is made has a beginning of its duration. But it can be proved demonstratively that God is the effective cause of the world; indeed this is asserted by the more approved philosophers. Therefore it can be demonstratively proved that the world began.

            Obj. 2: Further, if it is necessary to say that the world was made by God, it must therefore have been made from nothing or from something. But it was not made from something; otherwise the matter of the world would have preceded the world; against which are the arguments of Aristotle (De Coelo i), who held that heaven was ungenerated. Therefore it must be said that the world was made from nothing; and thus it has being after not being. Therefore it must have begun.

            Obj. 3: Further, everything which works by intellect works from some principle, as appears in all kinds of craftsmen. But God acts by intellect: therefore His work has a principle. The world, therefore, which is His effect, did not always exist.

            Obj. 4: Further, it appears clearly that certain arts have developed, and certain countries have begun to be inhabited at some fixed time. But this would not be the case if the world had been always. Therefore it is clear that the world did not always exist.

            Obj. 5: Further, it is certain that nothing can be equal to God. But if the world had always been, it would be equal to God in duration. Therefore it is certain that the world did not always exist.

            Obj. 6: Further, if the world always was, the consequence is that infinite days preceded this present day. But it is impossible to pass through an infinite medium. Therefore we should never have arrived at this present day; which is clearly false.

            Obj. 7: Further, if the world was eternal, generation also was eternal. Therefore one man was begotten of another in an infinite series. But the father is the efficient cause of the son (Phys. ii, text 5). Therefore in efficient causes there could be an infinite series, which is disproved (Metaph. ii, text 5).

            Obj. 8: Further, if the world and generation always were, there have been an infinite number of men. But man's soul is immortal: therefore an infinite number of human souls would actually now exist, which is impossible. Therefore it can be known with certainty that the world began, and not only is it known by faith.

            On the contrary, The articles of faith cannot be proved demonstratively, because faith is of things "that appear not" (Heb. 11:1). But that God is the Creator of the world: hence that the world began, is an article of faith; for we say, "I believe in one God," etc. Again, Gregory says (Hom. i in Ezech.), that Moses prophesied of the past, saying, "In the beginning God created heaven and earth": in which words the newness of the world is stated. Therefore the newness of the world is known only by revelation; and therefore it cannot be proved demonstratively.

            I answer that, By faith alone do we hold, and by no demonstration can it be proved, that the world did not always exist, as was said above of the mystery of the Trinity (Q. 32, A. 1). The reason of this is that the newness of the world cannot be demonstrated on the part of the world itself. For the principle of demonstration is the essence of a thing. Now everything according to its species is abstracted from "here" and "now"; accordingly it is said that universals are everywhere and always. Hence it cannot be demonstrated that man, or heaven, or a stone were not always. Likewise neither can it be demonstrated on the part of the efficient cause, which acts by will. For the will of God cannot be investigated by reason, except as regards those things which God must will of necessity; and what He wills about creatures is not among these, as was said above (Q. 19, A. 3). But the divine will can be displayed by revelation, on which faith rests. Hence it is an object of faith that the world began to exist, but not of demonstration or science. It is useful to consider this, so that no one, presuming to demonstrate what is of faith, should bring forward reasons that are unconvincing, so as to give occasion to unbelievers to laugh, thinking that on such grounds we believe things that are of faith.

            Reply Obj. 1: As Augustine says (De Civ. Dei xi, 4), the opinion of philosophers who asserted the eternity of the world was twofold. For some said that the substance of the world was not from God, which is an intolerable error; and therefore it is refuted by proofs that are cogent. Some, however, said that the world was eternal, although made by God. For they hold that the world has a beginning, not of time, but of creation, so that in a certain hardly intelligible way it was always made. "And they try to explain their meaning thus (De Civ. Dei x, 31): for as, if the foot were always in the dust from eternity, there would always be a footprint which without doubt was caused by him who trod on it, so also the world always was, because its Maker always existed." To understand this we must consider that the efficient cause, which acts by motion, of necessity precedes its effect in time; because the effect is only in the end of the action, and every agent must be the principle of action. But if the action is instantaneous and not successive, it is not necessary for the maker to be prior to the thing made in duration as appears in the case of illumination. Hence they say that it does not follow necessarily if God is the active cause of the world, that He should be prior to the world in duration; because creation, by which He produced the world, is not a successive change, as was said above (Q. 45, A. 2).

            Reply Obj. 2: Those who would say that the world was eternal, would say that the world was made by God from nothing, not that it was made after nothing, according to what we understand by the word creation, but that it was not made from anything; and so also some of them do not reject the word creation, as appears from Avicenna (Metaph. ix, text 4).

            Reply Obj. 3: This is the argument of Anaxagoras (as quoted in Phys. viii, text 15). But it does not lead to a necessary conclusion, except as to that intellect which deliberates in order to find out what should be done, which is like movement. Such is the human intellect, but not the divine intellect (Q. 14, AA. 7, 12).

            Reply Obj. 4: Those who hold the eternity of the world hold that some region was changed an infinite number of times, from being uninhabitable to being inhabitable and "vice versa," and likewise they hold that the arts, by reason of various corruptions and accidents, were subject to an infinite variety of advance and decay. Hence Aristotle says (Meteor. i), that it is absurd from such particular changes to hold the opinion of the newness of the whole world.

            Reply Obj. 5: Even supposing that the world always was, it would not be equal to God in eternity, as Boethius says (De Consol. v, 6); because the divine Being is all being simultaneously without succession; but with the world it is otherwise.

            Reply Obj. 6: Passage is always understood as being from term to term. Whatever bygone day we choose, from it to the present day there is a finite number of days which can be passed through. The objection is founded on the idea that, given two extremes, there is an infinite number of mean terms.

            Reply Obj. 7: In efficient causes it is impossible to proceed to infinity per se [i.e., when they occur simultaneously]. Thus, there cannot be an infinite number of causes that are per se required for a certain effect; for instance, that a stone be moved by a stick, the stick by the hand, and so on to infinity. But it is not impossible to proceed to infinity accidentally as regards efficient causes [i.e., when they occur through time]; for instance, if all the causes thus infinitely multiplied should have the order of only one cause, their multiplication being accidental, as an artificer acts by means of many hammers accidentally, because one after the other may be broken. It is accidental, therefore, that one particular hammer acts after the action of another; and likewise it is accidental to this particular man as generator to be generated by another man; for he generates as a man, and not as the son of another man. For all men generating hold one grade in efficient causes—viz. the grade of a particular generator. Hence it is not impossible for a man to be generated by man to infinity; but such a thing would be impossible if the generation of this man depended upon this man, and on an elementary body, and on the sun, and so on to infinity.

            Reply Obj. 8: Those who hold the eternity of the world evade this reason in many ways. For some do not think it impossible for there to be an actual infinity of souls, as appears from the Metaphysics of Algazel, who says that such a thing is an accidental infinity. But this was disproved above (Q. 7, A. 4). Some say that the soul is corrupted with the body. Some say that of all souls only one will remain. But others, as Augustine says [*Serm. xiv, De Temp. 4, 5; De Haeres., haeres. 46; De Civ. Dei xii. 13], asserted on this account a circuit of souls—viz. that souls separated from their bodies return again thither after a course of time; a fuller consideration of which matters will be given later (Q. 75, A. 2; Q. 118, A. 6). But be it noted that this argument considers only a particular case. Hence one might say that the world was eternal, or at least some creature, as an angel, but not man. But we are considering the question in general, as to whether any creature can exist from eternity.




Argument for Divine Simplicity: The Act of Composing is prior to any Composite (CT 1.9)

The first mover must be simple. For any composite being must contain two factors that are related to each other as potentiality to actuality. But in the first mover, which is altogether immobile, all combination of potentiality and actuality is impossible, because whatever is in potentiality is, by that very fact, movable. Accordingly the first mover cannot be composite.

            Moreover, something has to exist prior to any composite, since composing elements are by their very nature antecedent to a composite. Hence the first of all beings cannot be composite. Even within the order of composite beings we observe that the simpler things have priority. Thus elements are naturally prior to mixed bodies. Likewise, among the elements themselves, the first is fire, which is the simplest of all. Prior to all elements is the heavenly body, which has a simpler construction, since it is free from all contrariety. Hence the truth remains that the first of beings must be absolutely simple.


Whether God Is Altogether Simple? (ST 1.3.7)

            Objection 1: It seems that God is not altogether simple. For whatever is from God must imitate Him. Thus from the first being are all beings; and from the first good is all good. But in the things which God has made, nothing is altogether simple. Therefore neither is God altogether simple.

            Obj. 2: Further, whatever is best must be attributed to God. But with us that which is composite is better than that which is simple; thus, chemical compounds are better than simple elements, and animals than the parts that compose them. Therefore it cannot be said that God is altogether simple.

            On the contrary, Augustine says (De Trin. iv, 6,7): "God is truly and absolutely simple."

            I answer that, The absolute simplicity of God may be shown in many ways. First, from the previous articles of this question. For there is neither composition of quantitative parts in God, since He is not a body; nor composition of matter and form; nor does His nature differ from His being (suppositum); nor His essence from His existence; neither is there in Him composition of genus and difference, nor of subject and accident. Therefore, it is clear that God is in no way composite, but is altogether simple. Secondly, because every composite is posterior to its component parts, and is dependent on them; but God is the first being, as shown above (Q. 2, A. 3). Thirdly, because every composite has a cause, for things in themselves different cannot unite unless something causes them to unite. But God is uncaused, as shown above (Q. 2, A. 3), since He is the first efficient cause. Fourthly, because in every composite there must be potentiality and actuality; but this does not apply to God; for either one of the parts actuates another, or at least all the parts are potential to the whole. Fifthly, because nothing composite can be predicated of any single one of its parts. This is evident in a whole made up of dissimilar parts; for no part of a man is a man, nor any of the parts of the foot, a foot. But in wholes made up of similar parts, although something which is predicated of the whole may be predicated of a part (as a part of the air is air, and a part of water, water), nevertheless certain things are predicable of the whole which cannot be predicated of any of the parts; for instance, if the whole volume of water is two cubits, no part of it can be two cubits. Thus in every composite there is something which is not it itself. But, even if this could be said of whatever has a form, viz. that it has something which is not it itself, as in a white object there is something which does not belong to the essence of white; nevertheless in the form itself, there is nothing besides itself. So, since God is absolute form, or rather absolute being, He can be in no way composite. Hilary implies this argument, when he says (De Trin. vii): "God, Who is strength, is not made up of things that are weak; nor is He Who is light, composed of things that are dim."

            Reply Obj. 1: Whatever is from God imitates Him, as caused things imitate the first cause. But it is of the essence of a thing to be in some sort composite; because at least its existence differs from its essence, as will be shown hereafter, (Q. 4, A. 3).

            Reply Obj. 2: With us composite things are better than simple things, because the perfections of created goodness cannot be found in one simple thing, but in many things. But the perfection of divine goodness is found in one simple thing (QQ. 4, A. 1, and 6, A. 2).


Conceiving a Simple Thing as Composite (ST 1.3.3.R1)

We can speak of simple things only as though they were like the composite things from which we derive our knowledge. Therefore in speaking of God, we use concrete nouns to signify His subsistence, because with us only those things subsist which are composite; and we use abstract nouns to signify His simplicity. In saying therefore that Godhead, or life, or the like are in God, we indicate the composite way in which our intellect understands, but not that there is any composition in God.


Simplicity implies Perfection (ST 1.4.1)

As the Philosopher relates (Metaph. xii), some ancient philosophers, namely, the Pythagoreans and Leucippus, did not predicate "best" and "most perfect" of the first principle. The reason was that the ancient philosophers considered only a material principle; and a material principle is completely imperfect. For since matter as such is merely potential, the first material principle must be simply potential, and thus most imperfect. Now God is the first principle, not material, but in the order of efficient cause, which must be most perfect. For just as matter, as such, is merely potential, an agent, as such, is in the state of actuality. Hence, the first active principle must be most actual, and therefore most perfect; for a thing is perfect in proportion to its state of actuality, because we call that perfect which lacks nothing of the manner of its perfection.


All Perfections Found in Creatures exist most Highly in God (CT 21)

The further inference clearly follows that all perfections found in anything at all must originally and superabundantly be present in God. Whatever moves something toward perfection, must first possess in itself the perfection it confers on others. Thus a teacher has in his own mind the knowledge he hands on to others. Therefore, since God is the first mover, and moves all other beings toward their perfections, all perfections found in things must pre-exist in Him superabundantly.

            Besides, whatever has a particular perfection but lacks another perfection, is contained under some genus or species. For each thing is classed under a genus or a species by its form, which is the thing’s perfection. But what is placed under species and genus cannot be infinite in essence; for the ultimate difference by which it is placed in a species necessarily closes off its essence. Hence the very ratio or description that makes a species known is called its definition, or even finis. Therefore, if the divine essence is infinite, it cannot possess merely the perfection of some genus or species and be lacking in other perfections; the perfections of all genera or species must be in God.


Unity of All Perfections In God (CT 22)

If we gather together the various points established thus far, we perceive that all perfections in God are in reality one. We have shown above that God is simple. But where there is simplicity, there can be no distinction among the perfections that are present. Hence, if the perfections of all things are in God, they cannot be distinct in Him. Accordingly they are all one in Him.

            This will become evident to anyone who reflects on our cognitive powers. A higher faculty has a unified knowledge of all that is known through the lower faculties according to diverse aspects. All that the sight, the hearing, and the other senses perceive, the intellect judges with the one, simple power that belongs to it. Something similar appears in the sciences. The lower sciences are multiplied in accord with the various classes of beings that constitute their objects. Yet one science which holds the primacy among them is interested in all classes of beings. This is known as first philosophy. The same situation is observed in civil power; in the royal power, which is but one, are included all the powers that are distributed through various offices within the jurisdiction of the kingdom. In the same way perfections, which in lower things are multiplied according to the diversity of these things, must be united in the pinnacle of being, that is, in God.


God’s Simplicity Not Contradicted by The Multiplicity Of Names Applied To Him (CT 24)

This enables us to perceive the reason for the many names that are applied to God, even though in Himself He is absolutely simple. Since our intellect is unable to grasp His essence as it is in itself, we rise to a knowledge of that essence from the things that surround us. Various perfections are discerned in these things, the root and origin of them all being one in God, as has been shown. Since we cannot name an object except as we understand it (for names are signs of things understood), we cannot give names to God except in terms of perfections perceived in other things that have their origin in Him. Since these perfections are multiple in such things, we must assign many names to God. If we saw His essence as it is in itself, a multiplicity of names would not be required; our idea of it would be simple, just as His essence is simple. This vision we hope for in the day of our glory; for, according to Zacharias 14:9, “In that day there shall be one Lord, and His name shall be one.”


The Names of God Not Synonymous (CT 25)

In this connection three observations are in order. The first is that the various names applied to God are not synonymous, even though they signify what is in reality the same thing in God. In order to be synonymous, names must signify the same thing, and besides must stand for the same intellectual conception. But when the same object is signified according to diverse aspects, that is, notions which the mind forms of that object, the names are not synonymous. For then the meaning is not quite the same, since names directly signify intellectual conceptions, which are likenesses of things. Therefore, since the various names predicated of God signify the various conceptions our mind forms of Him, they are not synonymous, even though they signify absolutely the same thing.


Impossibility of Defining God (CT 26)

A second point is this: since our intellect does not adequately grasp the divine essence in any of the conceptions which the names applied to God signify, the definitions of these terms cannot define what is in God. That is, any definition we might formulate of the divine wisdom would not be a definition of the divine power, and so on regarding other attributes.

            The same is clear for another reason. A definition is made up of genus and specific differences, for what is properly defined is the species. But we have shown that the divine essence is not included under any genus or species. Therefore it cannot be defined.


Analogy of Terms Predicated of God and of Other Beings (CT 27)

The third point is that names applied to God and to other beings are not predicated either quite univocally or quite equivocally. They cannot be predicated univocally, because the definition of what is said of a creature is not a definition of what is said of God. Things predicated univocally must have the same definition.

            Nor are these names predicated in all respects equivocally. In the case of fortuitous equivocation, a name is attached to an object that has no relation to another object bearing the same name. Hence the reasoning in which we engage about one cannot be transferred to the other. But the names predicated of God and of other things are attributed to God according to some relation He has to those things; and in their case the mind ponders what the names signify. This is why we can transfer our’ reasoning about other things to God.

            Therefore such terms are not predicated altogether equivocally about God and about other things, as happens in fortuitous equivocation. Consequently they are predicated according to analogy, that is, according to their proportion to one thing. For, from the fact that we compare other things with God as their first origin, we attribute to God such names as signify perfections in other things. This clearly brings out the truth that, as regards the assigning of the names, such names are primarily predicated of creatures, inasmuch as the intellect that assigns the names ascends from creatures to God. But as regards the thing signified by the name, they are primarily predicated of God, from whom the perfections descend to other beings.


What Names can be predicated of God (SCG 1.30)

We may further consider what may be said or not said of God, or what may be said of Him only, what again may be said of God and at the same time also of other beings. Inasmuch as every perfection of the creature may be found in God, although in another and a more excellent way, it follows that whatever names absolutely denote perfection without defect, are predicated of God and of other beings, as for instance, “goodness,” “wisdom,” “being,” and the like. But whatever names denote such perfection with the addition of a manner proper to creatures, cannot be predicated of God except by way of similitude and metaphor, by which the attributes of one thing are adapted to another, as when a man is called a “block” for the denseness of his understanding. Of this sort are all names imposed to denote the species of a created thing, as “man,” and “stone”: for to every species is due its own proper manner of perfection and being. In like manner also whatever names denote properties that are caused in things by their proper specific principles, cannot be predicated of God otherwise than metaphorically. But the names that express such perfections with that manner of supereminent excellence in which they pertain to God, are predicated of God alone, as for instance, “Sovereign Good”, “First Being”, and the like.


Whether What Is Said of God and of Creatures Is Univocally Predicated of Them? (ST 1.13.5)

            Objection 1: It seems that the things attributed to God and creatures are univocal. For every equivocal term is reduced to the univocal, as many are reduced to one; for if the name "dog" be said equivocally of the barking dog, and of the dogfish, it must be said of some univocally—viz. of all barking dogs; otherwise we proceed to infinitude. Now there are some univocal agents which agree with their effects in name and definition, as man generates man; and there are some agents which are equivocal, as the sun which causes heat, although the sun is hot only in an equivocal sense. Therefore it seems that the first agent to which all other agents are reduced, is an univocal agent: and thus what is said of God and creatures, is predicated univocally.

            Obj. 2: Further, there is no similitude among equivocal things. Therefore as creatures have a certain likeness to God, according to the word of Genesis (Gen. 1:26), "Let us make man to our image and likeness," it seems that something can be said of God and creatures univocally.

            Obj. 3: Further, measure is homogeneous with the thing measured. But God is the first measure of all beings. Therefore God is homogeneous with creatures; and thus a word may be applied univocally to God and to creatures.

            On the contrary, whatever is predicated of various things under the same name but not in the same sense, is predicated equivocally. But no name belongs to God in the same sense that it belongs to creatures; for instance, wisdom in creatures is a quality, but not in God. Now a different genus changes an essence, since the genus is part of the definition; and the same applies to other things. Therefore whatever is said of God and of creatures is predicated equivocally.

            Further, God is more distant from creatures than any creatures are from each other. But the distance of some creatures makes any univocal predication of them impossible, as in the case of those things which are not in the same genus. Therefore much less can anything be predicated univocally of God and creatures; and so only equivocal predication can be applied to them.

            I answer that, Univocal predication is impossible between God and creatures [i.e., words used exactly the same way]. The reason of this is that every effect which is not an adequate result of the power of the efficient cause, receives the similitude of the agent not in its full degree, but in a measure that falls short, so that what is divided and multiplied in the effects resides in the agent simply, and in the same manner; as for example the sun by exercise of its one power produces manifold and various forms in all inferior things. In the same way, as said in the preceding article, all perfections existing in creatures divided and multiplied, pre-exist in God unitedly. Thus when any term expressing perfection is applied to a creature, it signifies that perfection distinct in idea from other perfections; as, for instance, by the term "wise" applied to man, we signify some perfection distinct from a man's essence, and distinct from his power and existence, and from all similar things; whereas when we apply to it God, we do not mean to signify anything distinct from His essence, or power, or existence. Thus also this term "wise" applied to man in some degree circumscribes and comprehends the thing signified; whereas this is not the case when it is applied to God; but it leaves the thing signified as incomprehended, and as exceeding the signification of the name. Hence it is evident that this term "wise" is not applied in the same way to God and to man. The same rule applies to other terms. Hence no name is predicated univocally of God and of creatures.

            Neither, on the other hand, are names applied to God and creatures in a purely equivocal sense [i.e., completely different from each other], as some have said. Because if that were so, it follows that from creatures nothing could be known or demonstrated about God at all; for the reasoning would always be exposed to the fallacy of equivocation. Such a view is against the philosophers, who proved many things about God, and also against what the Apostle says: "The invisible things of God are clearly seen being understood by the things that are made" (Rom. 1:20). Therefore it must be said that these names are said of God and creatures in an analogous sense, i.e., according to proportion.

            Now names are thus used in two ways. The first is according as many things are proportionate to one, thus for example "healthy" predicated of medicine and urine in relation and in proportion to health of a body, of which the former is the sign and the latter the cause. The second is according as one thing is proportionate to another, thus "healthy" is said of medicine and animal, since medicine is the cause of health in the animal body. In this way some things are said of God and creatures analogically, and not in a purely equivocal nor in a purely univocal sense. For we can name God only from creatures (A. 1). Thus whatever is said of God and creatures, is said according to the relation of a creature to God as its principle and cause, wherein all perfections of things pre-exist excellently. Now this manner of community of idea is a mean between pure equivocation and simple univocation. For in analogies the idea is not, as it is in univocals, one and the same, yet it is not totally diverse as in equivocals; but a term which is thus used in a multiple sense signifies various proportions to some one thing; thus "healthy" applied to urine signifies the sign of animal health, and applied to medicine signifies the cause of the same health.

            Reply Obj. 1: Although equivocal predications must be reduced to univocal, still in actions, the non-univocal agent must precede the univocal agent. For the non-univocal agent is the universal cause of the whole species, as for instance the sun is the cause of the generation of all men; whereas the univocal agent is not the universal efficient cause of the whole species (otherwise it would be the cause of itself, since it is contained in the species), but is a particular cause of this individual which it places under the species by way of participation. Therefore the universal cause of the whole species is not an univocal agent; and the universal cause comes before the particular cause. But this universal agent, while it is not univocal, nevertheless is not altogether equivocal, otherwise it could not produce its own likeness, but rather it is to be called an analogical agent, as all univocal predications are reduced to one first non-univocal analogical predication, which is being.

            Reply Obj. 2: The likeness of the creature to God is imperfect, for it does not represent one and the same generic thing (Q. 4, A. 3).

            Reply Obj. 3: God is not the measure proportioned to things measured; hence it is not necessary that God and creatures should be in the same genus.

            The arguments adduced in the contrary sense prove indeed that these names are not predicated univocally of God and creatures; yet they do not prove that they are predicated equivocally.




Whether There Are Ideas (Forms) in God’s Mind? (ST 1.15.1)

            Objection 1: It seems that there are no ideas. For Dionysius says (Div. Nom. vii), that God does not know things by ideas. But ideas are for nothing else except that things may be known through them. Therefore there are no ideas.

            Obj. 2: Further, God knows all things in Himself, as has been already said (Q. 14, A. 5). But He does not know Himself through an idea; neither therefore other things.

            Obj. 3: Further, an idea is considered to be the principle of knowledge and action. But the divine essence is a sufficient principle of knowing and effecting all things. It is not therefore necessary to suppose ideas.

            On the contrary, Augustine says (Octog. Tri. Quaest. qu. xlvi), "Such is the power inherent in ideas, that no one can be wise unless they are understood."


The Forms are in God’s Mind which he Uses in Creating the World

            I answer that, It is necessary to suppose ideas in the divine mind. For the Greek word Idea is in Latin Forma. Hence by ideas are understood the forms of things, existing apart from the things themselves. Now the form of anything existing apart from the thing itself can be for one of two ends: either to be the type of that of which it is called the form, or to be the principle of the knowledge of that thing, inasmuch as the forms of things knowable are said to be in him who knows them. In either case we must suppose ideas, as is clear for the following reason:

            In all things not generated by chance, the form must be the end of any generation whatsoever. But an agent does not act on account of the form, except in so far as the likeness of the form is in the agent, as may happen in two ways. For in some agents the form of the thing to be made pre-exists according to its natural being, as in those that act by their nature; as a man generates a man, or fire generates fire. Whereas in other agents (the form of the thing to be made pre-exists) according to intelligible being, as in those that act by the intellect; and thus the likeness of a house pre-exists in the mind of the builder. This may be called the idea of the house, since the builder intends to build his house like to the form conceived in his mind. As then the world was not made by chance, but by God acting by His intellect, as will appear later (Q. 46, A. 1), there must exist in the divine mind a form to the likeness of which the world was made. In this the notion of an idea consists.

            Reply Obj. 1: God does not understand things according to an idea existing outside Himself. Thus Aristotle (Metaph. ix) rejects the opinion of Plato, who held that ideas existed of themselves, and not in the intellect.

            Reply Obj. 2: Although God knows Himself and all else by His own essence, yet His essence is the operative principle of all things, except of Himself. It has therefore the nature of an idea with respect to other things; though not with respect to Himself.

            Reply Obj. 3: God is the similitude of all things according to His essence; therefore an idea in God is identical with His essence.


Passive-Possible Human Intellect receives Particular Intelligible Forms of Material Things (CT 1.81)

As was stated above, the higher an intellectual substance is in perfection, the more universal are the intelligible forms it possesses. Of all the intellectual substances, consequently, the human intellect, which we have called possible , has forms of the least universality. This is the reason it receives its intelligible forms from sensible things.

            This can be made clear from another point of view. A form must have some proportion to the potentiality which receives it. Therefore, since of all intellectual substances man’s passive-possible intellect is found to be the closest to corporeal matter, its intelligible forms must, likewise, be most closely allied to material things.


Sense Faculties receive Particular Forms of Material Things (CT 1.82)

However, we must realize that forms in corporeal things are particular, and have a material existence. But in the intellect they are universal and immaterial. Our manner of understanding brings this out. That is, we apprehend things universally and immaterially. This way of understanding must conform to the intelligible species [i.e., mental representations] by which we understand. Consequently, since it is impossible to pass from one extreme to another without crossing what lies between, forms reaching the intellect from corporeal objects must pass through certain media.

            These are the sense faculties, which receive the forms of material things without their matter; what lodges in the eye is the species of the stone, but not its matter. However, the forms of things received into the sense faculties are particular; for we know only particular objects with our sense faculties. Hence man must be endowed with senses as a prerequisite to understanding. A proof of this is the fact that if a man is lacking in one of the senses, he has no knowledge of sensible objects that are apprehended by that sense. Thus a person born blind can have no knowledge of colors.


Active-Agent Intellect turns Particular Forms of Material Things into Universal Forms (CT 83)

This discussion brings out the truth that knowledge of things in our intellect is not caused by any participation or influence of forms that are intelligible in act and that subsist by themselves, as was taught by the Platonists and certain other philosophers who followed them in this doctrine. No, the intellect acquires such knowledge from sensible objects, through the intermediacy of the senses. However, since the forms of objects in the sense faculties are particular, as we just said, they are intelligible not in actuality, but only in potentiality. For the intellect understands nothing but universals. But what is in potentiality is not reduced to actuality except by some agent. Hence there must be some agent that causes the species existing in the sense faculties to be intelligible in actuality. The passive-possible intellect cannot perform this service, for it is in potentiality with respect to intelligible objects rather than active in giving them intelligible. Therefore we must assume some other intellect, which will cause species that are intelligible in potentiality to become intelligible in actuality, just as light causes colors that are potentially visible to be actually visible. This faculty we call the active-agent intellect, which we would not have to postulate if the forms of things were intelligible in actuality, as the Platonists held.

            To understand, therefore, we have need, first, of the passive-possible intellect which receives intelligible species, and secondly, of the active-agent intellect which makes things intelligible in actuality. Once the passive-possible intellect has been perfected by the intelligible species, it is called the habitual intellect (intellectus in habitu), for then it possesses intelligible species in such a way that it can use them at will. In other words, it possesses them in a fashion that is midway between pure potentiality and complete actuality. But when it has these species in full actuality, it is called the intellect in actuality. That is, the intellect actually understands a thing when the species of the thing is made the form of the passive-possible intellect. This is why we say that the intellect in actuality is the object actually understood.


Whether the Active Intellect is Something in the Soul? (ST 1.79.5)

We must say that in the soul is some power derived from a higher intellect, whereby it is able to light up the phantasms [i.e., sense perceptions]. We know this by experience, since we perceive that we abstract universal forms from their particular conditions, which is to make them actually intelligible. Now no action belongs to anything except through some principle formally inherent therein; as we have said above of the passive intellect (I:76:1). Therefore the power which is the principle of this action must be something in the soul. For this reason Aristotle compared the active intellect to light, which is something received into the air (De Anima iii, 5). Plato compared the separate intellect impressing the soul to the sun (as Themistius says in his commentary on De Anima iii). But the separate intellect, according to the teaching of our faith, is God Himself, Who is the soul's Creator, and only beatitude, as will be shown later on (I:90:3; I-II:3:7). Accordingly, the human soul derives its intellectual light from Him, according to Psalm 4:7, "The light of your appearance, Lord, is signed upon us."


Whether the Intellectual Soul Knows Material Things in the Eternal Types? (ST 1.84.5)

            Objection 1: It would seem that the intellectual soul does not know material things in the eternal types [i.e., Forms]. For that in which anything is known must itself be known more and previously. But the intellectual soul of man, in the present state of life, does not know the eternal types: for it does not know God in Whom the eternal types exist, but is "united to God as to the unknown," as Dionysius says (Myst. Theolog. i). Therefore the soul does not know all in the eternal types.


Forms Exist in God’s Mind, not Independently of God as Creative Substances

            I answer that, As Augustine says (De Doctr. Christ. ii, 11): "If those who are called philosophers said by chance anything that was true and consistent with our faith, we must claim it from them as from unjust possessors. For some of the doctrines of the heathens are spurious imitations or superstitious inventions, which we must be careful to avoid when we renounce the society of the heathens." Consequently whenever Augustine, who was infused with the doctrines of the Platonists, found in their teaching anything consistent with faith, he adopted it. Those things which he found contrary to faith he amended. Now Plato held, as we have said above (A. 4), that the forms of things exist in themselves apart from matter. He calls these ideas, by participation of which he said that our intellect knows all things. Thus, just as corporeal matter by participating the idea of a stone becomes a stone, so our intellect, by participating the same idea, has knowledge of a stone. But since it seems contrary to faith to maintain that forms of things themselves are creative substances (being outside the things themselves and apart from matter, as the Platonists held, asserting that per se life or per se wisdom, as Dionysius relates; Div. Nom. xi). Therefore Augustine, for the ideas defended by Plato, substituted the types of all creatures existing in the Divine mind, according to which types all things are made in themselves, and are known to the human soul (QQ. 83, qu. 46).


Humans Know Forms through Intellectual Light

            When, therefore, the question is asked: Does the human soul know all things in the eternal types? we must reply that one thing is said to be known in another in two ways. First, as in an object itself known; as one may see in a mirror the images of things reflected therein. In this way the soul, in the present state of life, cannot see all things in the eternal types; but the blessed who see God, and all things in Him, thus know all things in the eternal types. Secondly, one thing is said to be known in another as in a principle of knowledge: thus we might say that we see in the sun what we see by the sun. Thus we must say that the human soul knows all things in the eternal types, since by participation of these types we know all things. For the intellectual light itself which is in us, is nothing else than a participated likeness of the uncreated light, in which are contained the eternal types. Accordingly it is written (Ps. 4:6, 7), "Many say: Who shows us good things?" which question the Psalmist answers, "The light of your appearance, Lord, is signed upon us," as though he were to say: By the seal of the Divine light in us, all things are made known to us.


Mental Representations of Physical Things (intelligible Species) Also required for Knowledge of Physical Things

            But since besides the intellectual light which is in us, intelligible species [mental representations of physical things], which are derived from things, are required in order for us to have knowledge of material things. Therefore this same knowledge is not due merely to a participation of the eternal types, as the Platonists held, maintaining that the mere participation of ideas sufficed for knowledge. Accordingly, Augustine says (De Trin. iv, 16): "Although the philosophers prove by convincing arguments that all things occur in time according to the eternal types, were they able to see in the eternal types, or to find out from them how many kinds of animals there are and the origin of each? Did they not seek for this information from the story of times and places?"

            Thus, Augustine did not maintain that all things are known in their "eternal types" or in the "unchangeable truth," as though the eternal types themselves were seen. This is clear when he says (QQ. 83, qu. 46) that "not each and every rational soul can be said to be worthy of that vision," namely, of the eternal types, "but only those that are holy and pure," such as the souls of the blessed.

            From what has been said the objections are easily solved.


Whether Intellectual Knowledge Is Derived from Sensible Things? (ST 1.84.6)


Democritus: Knowledge of Physical Things Caused by Image Particles from Sensible Objects

            I answer that, On this point the philosophers held three opinions. Democritus held that "all knowledge is caused by images issuing from the bodies we think of and entering into our souls," as Augustine says in his letter to Dioscorus (cxviii, 4). Aristotle says (De Somn. et Vigil.) that Democritus held that knowledge is caused by a "discharge of images." And the reason for this opinion was that both Democritus and the other early philosophers did not distinguish between intellect and sense, as Aristotle relates (De Anima iii, 3). Consequently, since the sense is affected by the sensible, they thought that all our knowledge is affected by this mere impression brought about by sensible things. This impression Democritus held to be caused by a discharge of images.


Plato: Knowledge of Physical Things comes from Forms not from Sensible Objects

            Plato, on the other hand, held that the intellect is distinct from the senses, and that it is an immaterial power not making use of a corporeal organ for its action. Since the incorporeal cannot be affected by the corporeal, he held that intellectual knowledge is not brought about by sensible things affecting the intellect, but by separate intelligible forms being participated by the intellect, as we have said above (AA. 4 ,5). Moreover he held that sense is a power operating of itself. Consequently neither is sense, since it is a spiritual power, affected by the sensible: but the sensible organs are affected by the sensible, the result being that the soul is in a way roused to form within itself the species of the sensible. Augustine seems to touch on this opinion (Gen. ad lit. xii, 24) where he says that the "body feels not, but the soul through the body, which it makes use of as a kind of messenger, for reproducing within itself what is announced from without." Thus according to Plato, neither does intellectual knowledge proceed from sensible knowledge, nor sensible knowledge exclusively from sensible things; but these rouse the sensible soul to the sentient act, while the senses rouse the intellect to the act of understanding.


Aristotle: Perceptions of Physical Things are received by the Passive-Possible intellect, which are then made Intelligible through the Active-Agent Intellect

            Aristotle chose a middle course. For, with Plato he agreed that intellect and sense are different. But he held that the sense does not have its proper operation without the cooperation of the body; thus, to feel is not an act of the soul alone, but of the "composite." He held the same in regard to all the operations of the sensitive part. Since, therefore, it is not unreasonable that the sensible objects which are outside the soul should produce some effect in the "composite," Aristotle agreed with Democritus. That is, the operations of the sensitive part are caused by the impression of the sensible on the sense: not by a discharge, as Democritus said, but by some kind of operation. For Democritus maintained that every operation is by way of a discharge of atoms, as we gather from De Gener. i, 8. But Aristotle held that the intellect has an operation which is independent of the body's cooperation. Now nothing corporeal can make an impression on the incorporeal. Therefore in order to cause the intellectual operation according to Aristotle, the impression caused by the sensible does not suffice, but something more noble is required, for "the agent is more noble than the patient," as he says (De Gener. i, 5). Indeed, it is not in the sense that the intellectual operation is effected in us by the mere impression of some superior beings, as Plato held. Rather, it is the higher and more noble agent which he calls the active intellect, of which we have spoken above (Q. 79, AA. 3, 4) that causes the phantasms received from the senses to be actually intelligible, by a process of abstraction.

            According to this opinion, then, on the part of the phantasms, intellectual knowledge is caused by the senses. But since the phantasms cannot of themselves affect the passive intellect, and require to be made actually intelligible by the active intellect, it cannot be said that sensible knowledge is the total and perfect cause of intellectual knowledge, but rather that it is in a way the material cause.




Voluntariness of God’s Activity (CT 96)

The truth set forth in the preceding chapter also discloses the fact that God has brought things into existence not through any necessity of His nature but by His will. A single natural agent produces immediately but one effect, whereas a voluntary, agent can produce a variety of effects. The reason for this is that every agent acts in virtue of its form. The natural form, by which a cause operates naturally, is limited to one for each agent. But intellectual forms, by which an agent operates through his will, are many. Therefore, since many things are immediately produced by God, as we have just shown, God evidently produces things by His will, and not under the impulse of natural necessity.

            Besides, in the order of causes, an agent operating through intellect and will is prior to an agent operating by the necessity of its nature. For an agent operating through his will predetermines for himself the end for the sake of which he acts, whereas a natural cause operates on account of an end predetermined for it by another. But, as is clear from all that has gone before, God is the first agent. Hence He acts through His will, and not by a necessity of His nature.

            Moreover, we demonstrated above that God is infinite in power. Consequently He is not determined to this or that effect, but is undetermined with regard to all effects. But what is undetermined regarding various effects, is determined to produce one of them by desire or by the determination of the will. Thus a man who is free to walk or not to walk, walks when he wills. Hence effects proceed from God according to the determination of His will. So He acts, not by a necessity of His nature, but by His will. This is why the Catholic faith calls the omnipotent God not only “Creator,” but also “Maker.” For making is properly the action of an artificer who operates by his will. Since every voluntary agent acts in virtue of the conception of his intellect, which is called his word, as we indicated above, and since the Word of God is His Son, the Catholic faith professes that “all things were made” by the Son.


Human Free Will Rationally Directed towards Good (SCG 2.48)

Some agents are without liberty of judgement, either because they have no judgement at all, as is the case with things that have no knowledge, such as stones and plants, or because they have a judgement naturally determined to one effect, such as irrational animals. For by natural calculation the sheep judges that the wolf is harmful to it, and on this judgement runs from the wolf. But whatever agents have their judgement of things to be done without being determined by nature to one effect, they must have free will. Such are all intelligent agents. For the understanding apprehends not only this or that good, but good itself in general. Hence, since it is through the idea in apprehension that the understanding moves the will; and in all things the motive, or moving power, and the object moved must be proportioned to one another; it follows that the will of an intelligent subsistent being is not determined by nature except to good in general. Whatever therefore is presented to the will under the specific notion of good (sub ratione boni), the will may incline to it, without let or hindrance from any natural determination to the contrary. Therefore all intelligent agents have free will, arising out of the judgement of the understanding; and free will is defined as a free judgement on the matter of a specific notion, or general concept.


Human Intellect and Will Moved by God (CT 129)

Everything that is changeable and multiform is traced back, as to its cause, to some first principle that is immobile and is one. Since man’s intellect and will are clearly changeable and multiform, they must be reduced to some higher cause that is immobile and uniform. The heavenly bodies are not the cause to which they are reduced, as we have shown; therefore they must be reduced to yet higher causes.

            In this matter the case of the intellect differs from that of the will. The act of the intellect is brought about by the presence of the things understood in the intellect; but the act of the will is accounted for by the inclination of the will toward the things willed. Thus the intellect is adapted by its nature to be perfected by something external that is related to it as act to potentiality. Hence man can be aided to elicit an act of the intellect by anything external that is more perfect in intelligible being: not only by God but also by an angel or even by a man who is better informed; but differently in each instance. A man is helped to understand by a man when one of them proposes to the other an intelligible object not previously contemplated; but not in such a way that the light of the intellect of one man is perfected by the other, because each of these natural lights is in one and the same species.

            But the natural light of an angel is by nature of a higher excellence than the natural light of man, and so an angel can aid a man to understand, not only on the part, of the object proposed to him by the angel, but also on the part of the light that is strengthened by the angel’s light. However, man’s natural light does not come from an angel, for the nature of the rational soul, which receives existence through creation, is produced by God alone.

            God helps man to understand, not only on the part of the object proposed by God to man, or by an increase of light, but also by the very fact that man’s natural light, which is what makes him intellectual, is from God. Moreover, God Himself is the first truth from which all other truth has its certitude, just as secondary propositions in demonstrative sciences derive their certitude from primary propositions. For this reason nothing can become certain for the intellect except through God’s influence, just as conclusions do not achieve certitude in science except in virtue of primary principles.

            With regard to the will, its act is a certain impulse flowing from the interior to the exterior, and has much in common with natural tendencies. Accordingly, as natural tendencies are placed in natural things exclusively by the cause of their nature, the act of the will is from God alone, for He alone is the cause of a rational nature endowed with will. Therefore, if God moves man’s will, this is evidently not opposed to freedom of choice, just as God’s activity in natural things is not contrary to their nature. Both the natural inclination and the voluntary inclination are from God; each of them issues in action according to the condition of the thing to which it pertains. God moves things in a way that is consonant with their nature.

            This exposition brings out the fact that heavenly bodies can exert an influence on the human body and its bodily powers, as they can in the case of other bodies. But they cannot do the same with regard to the intellect, although an intellectual creature can. God alone can touch the will.


God Governs the World by God through Secondary Causes and is Present Within Them (CT 130)

Second causes do not act except through the power of the first cause; thus instruments operate under the direction of art. Consequently all the agents through which God carries out the order of His government, can act only through the power of God Himself. The action of any of them is caused by God, just as the movement of a mobile object is caused by the motion of the mover. In such event the mover and the movement must be simultaneous. Hence God must be inwardly present to any agent as acting therein whenever He moves the agent to act.

            Another point: not only the action of secondary agents but their very existence is caused by God, as was shown above. However, we are not to suppose that the existence of things is caused by God in the same way as the existence of a house is caused by its builder. When the builder departs, the house still remains standing. For the builder causes the existence of the house only in the sense that he works for the existence of the house as a house. Such activity is, indeed, the constructing of the house, and thus the builder is directly the cause of the becoming of the house, a process that ceases when he desists from his labors. But God is directly, by Himself, the cause of very existence, and communicates existence to all things just as the sun communicates light to the air and to whatever else is illuminated by the sun. The continuous shining of the sun is required for the preservation of light in the air; similarly God must unceasingly confer existence on things if they are to persevere in existence. Thus all things are related to God as an object made is to its maker, and this not only so far as they begin to exist, but so far as they continue to exist. But a maker and the object made must be simultaneous, just as in the case of a mover and the object moved. Hence God is necessarily present to all things to the extent that they have existence. But existence is that which is the most intimately present in all things. Therefore God must be in all things.

            Moreover, whoever, through the agency of intermediate causes, carries out the order he has foreseen, must know and arrange the effects of these intermediate causes. Otherwise the effects would occur outside the order he has foreseen. The prearranged plan of a governor is more perfect in proportion as his knowledge and design descend to details. For if any detail escapes the advertence of the governor, the disposition of that detail will elude his foresight. We showed above that all things are necessarily subject to divine providence; and divine providence must evidently be most perfect, because whatever is predicated of God must befit Him in the highest possible degree. Consequently the ordinations of His providence must extend to the most minute effects.


God Governs through Secondary Causes, but Arranges All Particulars Himself (CT 131)

In the light of the foregoing, it is clear that, although God’s government of things is effected through the agency of secondary causes, as far as the arrangement of His providence is concerned, yet the plan itself or ordination of divine providence extends directly to all details. In arranging all matters from first to last, God does not turn over to others the ordering of the final particulars. Men act thus because of the limitations of their knowledge, which cannot at any one time take in many items. This is why higher rulers personally take charge of great concerns, and entrust the management of unimportant affairs to others. But God can take cognizance of a multitude of things simultaneously, as was indicated above. Hence the fact that He attends to the slightest details does not keep Him from organizing the weightiest matters.


Objections to God’s Particular Providence (CT 132)

Some may think that details are not regulated by God. For no one carries out anything in his planning unless he has knowledge of it. But knowledge of particulars may well seem to be lacking in God, for the reason that particulars are known, not by the intellect, but by the senses. God, who is wholly incorporeal, can have no sense knowledge, but only intellectual knowledge. Consequently details may seem to lie outside the scope of divine providence.

            Moreover, details are infinite, and knowledge of infinity is impossible, since the infinite as such is unknown. Therefore details seemingly escape the divine knowledge and providence.

            Again, many particulars are contingent. But certain knowledge of such objects is out of the question. Accordingly, since God’s knowledge must be absolutely certain, it seems that details are not known or regulated by God.

            Besides, particulars do not all exist simultaneously, for some things decay only to have others take their place. But there can be no knowledge of non-existent things. Hence, if God has knowledge of details, there must be some things which He begins and ceases to know, and this involves the further consequence that He is mutable. Apparently, therefore, He does not know and dispose particulars.


Solution of The Foregoing Objections (CT 133)

These objections are easily answered if we but penetrate to the truth of the matter. God knows Himself perfectly, and therefore He must have knowledge of all that exists in Himself in any manner whatever. Since every essence and power of created being is from Him, and since whatever comes from anyone exists virtually in him, we necessarily conclude that in knowing Himself He knows the essence of created being and whatever is virtually contained in the latter. Thus He knows all particulars that are virtually in Himself and in all His other causes.

            The knowledge possessed by the divine intellect is not like our knowledge, as the first objection urged. Our intellect derives knowledge of things through the species it abstracts, and these are the likenesses of forms and not of matter or of material dispositions, which are principles of individuation. Therefore our intellect cannot know particulars, but only universals. But the divine intellect knows things through its own essence, in which, as in the first principle of being, is virtually contained not only form, but matter. So God knows not only universals but also particulars.

            Likewise God is able to know an infinite number of objects, even though our intellect cannot know the infinite. Our intellect cannot actually contemplate many things at the same time. Hence, if it knew an infinite number of objects, it would have to review them one after another as it contemplated them, which is contrary to the very notion of infinity. However, our intellect can know infinity virtually and potentially, for example, it can know all the species of numbers or of proportions, seeing that it possesses an adequate principle for knowing all things. But God can know many things simultaneously, as was indicated above; and that by which He knows all things, namely, His essence, is an adequate principle for knowing, not only all that is, but all that can be. Therefore, as our intellect potentially and virtually knows those infinite objects for which it has a principle of cognition, so God actually contemplates all infinities.

            Furthermore, although corporeal and temporal particulars do not exist simultaneously, God surely has simultaneous knowledge of them. For He knows them according to His manner of being, which is eternal and without succession. Consequently, as He knows material things in an immaterial way, and many things in unity, so in a single glance He beholds objects that do not exist at the same time. So His knowledge of particulars does not involve the consequence that anything is added to, or subtracted from, His cognition.

            This also makes it clear that He has certain knowledge of contingent things. Even before they come into being, He sees them as they actually exist, and not merely as they will be in the future and as virtually present in their causes, in the way we are able to know some future things. Contingent things, regarded as virtually present in their causes with a claim to future existence, are not sufficiently determinate to admit of certain knowledge about them; but, regarded as actually possessing existence, they are determinate, and hence certain knowledge of them is possible. Thus we can know with the certitude of ocular vision that Socrates is sitting while he is seated. With like certitude God knows, in His eternity, all that takes place throughout the whole course of time. For His eternity is in present contact with the whole course of time, and even passes beyond time. We may fancy that God knows the flight of time in His eternity, in the way that a person standing on top of a watchtower embraces in a single glance a whole caravan of passing travelers.


God’s Foreknowledge contains All Details and is Not Based on Causes (CT 134)

To know contingent futures in this way, as being actually in existence, that is, to have certitude about them, is evidently restricted to God alone, of whom eternity is truly and properly predicated. For this reason, certain prediction of future events is accounted a proof of divinity. This accords with Isaiah 41:23: “Show the things that are to come hereafter, and we shall know that ye are gods.” Knowledge of future events in their causes is, indeed, possible for others. Such knowledge, however, is not certain, but is rather conjectural, except as regards effects that necessarily flow from their causes. In this way a physician foretells future illnesses, and a sailor predicts storms.


God’s Existence in All Things by Power, Essence, and Presence (CT 135)

Thus there is no reason why God should not have knowledge of individual effects, or why He should not directly regulate them by Himself, even though He may carry them out through intermediate causes. However, in some fashion, in the very execution He is in immediate touch with all effects, to the extent that all intermediate causes operate in virtue of the first cause, so that in a certain way He Himself appears to act in them all. Thus all the achievements of secondary causes can be attributed to Him, as the effect produced by a tool is ascribed to the artisan; when we say that a smith makes a knife, we are more correct than when we say that a hammer did it. God is also in immediate contact with all effects so far as He is per se the cause of their existence, and so far as everything is kept in being by Him.

            Corresponding to these three immediate types of influence, God is said to be in everything by essence, power, and presence. He is in everything by His essence inasmuch as the existence of each thing is a certain participation in the divine essence; the divine essence is present to every existing thing, to the extent that it has existence, as a cause is present to its proper effect. God is in all things by His power, inasmuch as all things operate in virtue of Him. God is in all things by His presence, inasmuch as He directly regulates and disposes all things.


Miracles diverge from Secondary Causes, but Not Contrary to Nature (CT 136)

The entire order of secondary causes, as well as their power, comes from God. He Himself, however, produces His effects not out of necessity, but by free will, as was shown above. Clearly, then, He can act outside the order of secondary causes, as when He cures those who are incurable from the standpoint of natural causality, or when He does something else of this kind that is not within the sphere of natural causes but is nevertheless consonant with the order of divine providence. What God occasionally does in this way, independently of the order of natural causes, is designed by Him for a definite end. When effects are thus produced by divine power outside the order of secondary causes, they are called miracles. For when we perceive an effect without knowing its cause, our wonder is excited (mirum est). God is a cause that is completely hidden from us. Therefore, when some effect is produced by Him outside the order of secondary causes known to us, it is called simply a miracle. But if an effect is produced by some other cause that is unknown to this or that person, it is not a miracle simply as such, but only with regard to him who is ignorant of the cause. Thus an event may appear marvelous to one person without seeming marvelous to another who is acquainted with its cause.

            To act in this way, outside the order of secondary causes, is possible for God alone, who is the founder of this order and is not confined to it. All other beings are subject to this order; and so God alone can work miracles, as the Psalmist says: “Who alone doth wonderful things” (Ps. 71:18). Therefore, when miracles are apparently worked by some creature, either they are not true miracles, but are effects produced by the power of natural agents, which may be concealed from us, as happens in the case of miracles produced by demons with their magical arts; or else, if they are true miracles, someone obtains the power to work them by praying to God. Since such miracles are produced exclusively by divine power, they are rightly appealed to in proof of the faith, which has God alone as its author. For a pronouncement issued by a man with a claim to divine authority, is never more properly attested than by works which God alone can perform.

            Although such miracles occur outside the order of secondary causes, we should not simply say that they are against nature. The natural order makes provision for the subjection of the lower to the activity of the higher. Thus effects brought about in lower bodies in consequence of the influence emanating from the heavenly bodies, are not said to be simply against nature, although they may at times be against the particular nature of this or that thing, as we observe in the movement of water in the ebb and flow of the tide, which is produced by the action of the moon. In the same way, effects produced in creatures by the action of God may seem to be against some particular order of secondary causes; yet they are in accord with the universal order of nature. Therefore miracles are not contrary to nature.


Fortuitous Events are Planned by God but do not Appear so to Us (CT 137)

Although all events, even the most trifling, are disposed according to God’s plan, as we have shown, there is nothing to prevent some things from happening by chance or accident. An occurrence may be accidental or fortuitous with respect to a lower cause when an effect not intended is brought about, and yet not be accidental or fortuitous with respect to a higher cause, inasmuch as the effect does not take place apart from the latter’s intention. For example, a master may send two servants to the same place, but in such a way that neither is aware of the mission of the other. Their meeting is accidental so far as each of them is concerned, but not as regards the master.

            So, when certain events occur apart from the intention of secondary causes, they are accidental or fortuitous with respect to those causes; and they may be said without further ado to be fortuitous, because effects are described simply in terms of their proximate causes. But if God’s point of view is considered, they are not fortuitous, but foreseen.




Eternal, Natural, Human and Divine Law (ST

A law is nothing else but a dictate of practical reason emanating from the ruler who governs a perfect community. Now it is evident, granted that the world is ruled by Divine Providence (as was stated in I:22:1 and I:22:2), that the whole community of the universe is governed by Divine Reason. Accordingly the very Idea of the government of things in God the Ruler of the universe, has the nature of a law. Since the Divine Reason's conception of things is not subject to time but is eternal, according to Proverbs 8:23, therefore it is that this kind of law must be called eternal.

            Since all things subject to Divine providence are ruled and measured by the eternal law, as was stated above (Article 1); it is evident that all things partake somewhat of the eternal law, in so far as, namely, from its being imprinted on them, they derive their respective inclinations to their proper acts and ends. Now among all others, the rational creature is subject to Divine providence in the most excellent way, in so far as it partakes of a share of providence, by being provident both for itself and for others. . . . It is therefore evident that the natural law is nothing else than the rational creature's participation of the eternal law.

            Just as, in the speculative reason, from naturally known indemonstrable principles, we draw the conclusions of the various sciences, the knowledge of which is not imparted to us by nature, but acquired by the efforts of reason, so too it is from the principles of the natural law, as from general and indemonstrable principles, that the human reason needs to proceed to the more particular determination of certain matters. These particular determinations, devised by human reason, are called human laws, provided the other essential conditions of law be observed.

            Besides the natural and the human law it was necessary for the directing of human conduct to have a Divine law. This is so for four reasons. First, because it is by law that man is directed how to perform his proper acts in view of his last end. . . . Secondly, because of the uncertainty of human judgment, especially on contingent and particular matters, different people form different judgments on human acts; accordingly also different and contrary laws result. In order, therefore, that man may know without any doubt what he ought to do and what he ought to avoid, it was necessary for man to be directed in his proper acts by a law given by God, for it is certain that such a law cannot err. Thirdly, because man can make laws in those matters of which he is competent to judge. . . . Fourthly, because, as Augustine says (De Lib. Arb. i, 5,6), human law cannot punish or forbid all evil deeds, . . . it was necessary for the Divine law to supervene, by which all sins are forbidden.


Whether the Natural Law Is a Habit? (ST

A thing may be called a habit in two ways. First, properly and essentially: and thus the natural law is not a habit. For it has been stated above (Q. 90, A. 1, ad 2) that the natural law is something appointed by reason, just as a proposition is a work of reason. Now that which a man does is not the same as that by which he does it: for he makes a becoming speech by the habit of grammar. Since then a habit is that by which we act, a law cannot be a habit properly and essentially.

            Secondly, the term habit may be applied to that which we hold by a habit: thus faith may mean that which we hold by faith. Accordingly, since the principles of the natural law are sometimes considered by reason actually, while sometimes they are in the reason only habitually, in this way the natural law may be called a habit. Thus, in speculative matters, the indemonstrable principles are not the habit itself by which we hold those principles, but are the principles the habit of which we possess.

            Reply Obj. 2: Synderesis [i.e., conscience] is said to be the law of our mind, because it is a habit containing the principles of the natural law, which are the first principles of human actions.


Whether the Natural Law Contains Several Principles, or Only One? (ST

Now a certain order is to be found in those things that are apprehended universally. For that which, before all else, falls under apprehension, is being, the notion of which is included in all things whatsoever a man apprehends. Accordingly the first indemonstrable principle is that "the same thing cannot be affirmed and denied at the same time," which is based on the notion of being and not-being: and on this principle all others are based, as is stated in Metaph. iv, text. 9. Now as being is the first thing that falls under the apprehension simply, so good is the first thing that falls under the apprehension of the practical reason, which is directed to action: since every agent acts for an end under the aspect of good. Consequently the first principle of practical reason is one founded on the notion of good, viz. that "good is that which all things seek after." Hence this is the first principle of law, that "good is to be done and pursued, and evil is to be avoided." All other principles of the natural law are based upon this: so that whatever the practical reason naturally apprehends as man's good (or evil) belongs to the principles of the natural law as something to be done or avoided.

            Since, however, good has the nature of an end, and evil, the nature of a contrary, hence it is that all those things to which man has a natural inclination, are naturally apprehended by reason as being good, and consequently as objects of pursuit, and their contraries as evil, and objects of avoidance. Accordingly, the order of the principles of the natural law follows the order of natural inclinations. Because in man there is first of all an inclination to good in accordance with the nature which he has in common with all substances: inasmuch as every substance seeks the preservation of its own being, according to its nature: and by reason of this inclination, whatever is a means of preserving human life, and of warding off its obstacles, belongs to the natural law. Secondly, there is in man an inclination to things that pertain to him more specially, according to that nature which he has in common with other animals: and in virtue of this inclination, those things are said to belong to the natural law, "which nature has taught to all animals" [Pandect. Just. I, tit. i], such as sexual intercourse, education of offspring and so forth. Thirdly, there is in man an inclination to good, according to the nature of his reason, which nature is proper to him: thus man has a natural inclination to know the truth about God, and to live in society: and in this respect, whatever pertains to this inclination belongs to the natural law; for instance, to shun ignorance, to avoid offending those among whom one has to live, and other such things regarding the above inclination.


Whether All Acts of Virtue Are Prescribed by the Natural Law? (

We may speak of virtuous acts in two ways: first, under the aspect of virtuous; secondly, as such and such acts considered in their proper species. If then we speak of acts of virtue, considered as virtuous, thus all virtuous acts belong to the natural law. For it has been stated (A. 2) that to the natural law belongs everything to which a man is inclined according to his nature. Now each thing is inclined naturally to an operation that is suitable to it according to its form: thus fire is inclined to give heat. Accordingly, since the rational soul is the proper form of man, there is in every man a natural inclination to act according to reason: and this is to act according to virtue. Consequently, considered thus, all acts of virtue are prescribed by the natural law: since each one's reason naturally dictates to him to act virtuously. But if we speak of virtuous acts, considered in themselves, i.e. in their proper species, thus not all virtuous acts are prescribed by the natural law: for many things are done virtuously, to which nature does not incline at first; but which, through the inquiry of reason, have been found by men to be conducive to well-living.


Whether the Natural Law Is the Same in All People? (ST

            I answer that, As stated above (AA. 2, 3), to the natural law belong those things to which a man is inclined naturally: and among these it is proper to man to be inclined to act according to reason. Now the process of reason is from the common to the proper, as stated in Phys. i. The speculative reason, however, is differently situated in this matter, from the practical reason. For, since the speculative reason is busied chiefly with necessary things, which cannot be otherwise than they are, its proper conclusions, like the universal principles, contain the truth without fail. The practical reason, on the other hand, is busied with contingent matters, about which human actions are concerned. Consequently, although there is necessity in the general principles, the more we descend to matters of detail, the more frequently we encounter defects. Accordingly then in speculative matters truth is the same in all men, both as to principles and as to conclusions: although the truth is not known to all as regards the conclusions, but only as regards the principles which are called common notions. But in matters of action, truth or practical rightness is not the same for all, as to matters of detail, but only as to the general principles: and where there is the same rightness in matters of detail, it is not equally known to all.

            It is therefore evident that, as regards the general principles whether of speculative or of practical reason, truth or rightness is the same for all, and is equally known by all. As to the proper conclusions of the speculative reason, the truth is the same for all, but is not equally known to all: thus it is true for all that the three angles of a triangle are together equal to two right angles, although it is not known to all. But as to the proper conclusions of the practical reason, neither is the truth or rightness the same for all, nor, where it is the same, is it equally known by all. Thus it is right and true for all to act according to reason: and from this principle it follows as a proper conclusion, that goods entrusted to another should be restored to their owner. Now this is true for the majority of cases: but it may happen in a particular case that it would be injurious, and therefore unreasonable, to restore goods held in trust; for instance, if they are claimed for the purpose of fighting against one's country. This principle will be found to fail the more, according as we descend further into detail, e.g. if one were to say that goods held in trust should be restored with such and such a guarantee, or in such and such a way; because the greater the number of conditions added, the greater the number of ways in which the principle may fail, so that it be not right to restore or not to restore.

            Consequently we must say that the natural law, as to general principles, is the same for all, both as to rightness and as to knowledge. But as to certain matters of detail, which are conclusions, as it were, of those general principles, it is the same for all in the majority of cases, both as to rightness and as to knowledge. Yet in some few cases it may fail, both as to rightness, by reason of certain obstacles (just as natures subject to generation and corruption fail in some few cases on account of some obstacle), and as to knowledge, since in some the reason is perverted by passion, or evil habit, or an evil disposition of nature. Thus formerly, theft, although it is expressly contrary to the natural law, was not considered wrong among the Germans, as Julius Caesar relates (De Bello Gall. vi).


Whether the Natural Law Can Be Changed? (ST

            Objection 1: It would seem that the natural law can be changed. Because on Ecclus. 17:9, "He gave them instructions, and the law of life," the gloss says: "He wished the law of the letter to be written, in order to correct the law of nature." But that which is corrected is changed. Therefore the natural law can be changed.

            Obj. 2: Further, the slaying of the innocent, adultery, and theft are against the natural law. But we find these things changed by God: as when God commanded Abraham to slay his innocent son (Gen. 22:2); and when he ordered the Jews to borrow and purloin the vessels of the Egyptians (Ex. 12:35); and when He commanded Hosea to take to himself "a wife of fornications" (Hosea 1:2). Therefore the natural law can be changed.

            Obj. 3: Further, Isidore says (Etym. 5:4) that "the possession of all things in common, and universal freedom, are matters of natural law." But these things are seen to be changed by human laws. Therefore it seems that the natural law is subject to change.

            On the contrary, It is said in the Decretals (Dist. v): "The natural law dates from the creation of the rational creature. It does not vary according to time, but remains unchangeable."

            I answer that, A change in the natural law may be understood in two ways. First, by way of addition. In this sense nothing hinders the natural law from being changed: since many things for the benefit of human life have been added over and above the natural law, both by the Divine law and by human laws.

            Secondly, a change in the natural law may be understood by way of subtraction, so that what previously was according to the natural law, ceases to be so. In this sense, the natural law is altogether unchangeable in its first principles: but in its secondary principles, which, as we have said (A. 4), are certain detailed proximate conclusions drawn from the first principles, the natural law is not changed so that what it prescribes be not right in most cases. But it may be changed in some particular cases of rare occurrence, through some special causes hindering the observance of such principles, as stated above (A. 4).

            Reply Obj. 1: The written law is said to be given for the correction of the natural law, either because it supplies what was wanting to the natural law; or because the natural law was perverted in the hearts of some men, as to certain matters, so that they esteemed those things good which are naturally evil; which perversion stood in need of correction.

            Reply Obj. 2: All men alike, both guilty and innocent, die the death of nature: which death of nature is inflicted by the power of God on account of original sin, according to 1 Kings 2:6: "The Lord kills and makes alive." Consequently, by the command of God, death can be inflicted on any man, guilty or innocent, without any injustice whatever. In like manner adultery is intercourse with another's wife; who is allotted to him by the law emanating from God. Consequently intercourse with any woman, by the command of God, is neither adultery nor fornication. The same applies to theft, which is the taking of another's property. For whatever is taken by the command of God, to Whom all things belong, is not taken against the will of its owner, whereas it is in this that theft consists. Nor is it only in human things, that whatever is commanded by God is right; but also in natural things, whatever is done by God, is, in some way, natural, as stated in the First Part, Q. 105, A. 6, ad 1.

            Reply Obj. 3: A thing is said to belong to the natural law in two ways. First, because nature inclines thereto: e.g. that one should not do harm to another. Secondly, because nature did not bring in the contrary: thus we might say that for man to be naked is of the natural law, because nature did not give him clothes, but art invented them. In this sense, "the possession of all things in common and universal freedom" are said to be of the natural law, because, to wit, the distinction of possessions and slavery were not brought in by nature, but devised by human reason for the benefit of human life. Accordingly the law of nature was not changed in this respect, except by addition.


Questions for Review

            1. According to Aquinas’s discussion of faith in two categories of divine truths (SCG 1.3), which truths about God are not discoverable to reason and which are?

            2. According to Aquinas discussion of “whether the existence of God is self-evident” (ST 1.2.1), what is his criticism of the ontological argument in his reply to objection 2?

            3. According to Aquinas discussion of “whether God exists” (ST 1.2.3), what are the criticisms of God’s existence in Objections 1 and 2?

            4. According to Aquinas discussion of “whether God exists” (ST 1.2.3), what briefly are the five ways for proving God’s existence?

            5. According to Aquinas discussion of “whether it is an article of faith that the world began” (ST 1.46.2), there are two types of efficient causes: per se (simultaneous) and accidentally (through time). What are his examples of each, and which can go back to infinity?

            6. According to Aquinas’s discussion of divine attributes and names, what are the main features of divine simplicity?

            7. According to Aquinas’s discussion of divine attributes and names, what is wrong with univocal descriptions of God (i.e., words that presumably have exactly the same meaning when describing both God and humans) and equivocal descriptions of God (i.e., words that presumably have entirely different meanings when describing both God and humans)?

            8. According to Aquinas’s discussion in “whether what is said of god and of creatures is univocally predicated of them” (ST 1.13.5), what are the main features of analogical descriptions of God?

            9. According to Aquinas’s discussion of “whether there are ideas in God’s mind” (ST 1.15.1), what are the main features of his view that the forms exist in God’s mind?

            10. According to Aquinas’s discussion of the forms and sensory perception (CT 1.81-2, ST 1.84.5) what are the main features of human sense perception of material objects?

            11. According to Aquinas’s discussion of “whether intellectual knowledge is derived from sensible things” (ST 1.84.5), what are the views of Democritus, Plato and Aristotle regarding our knowledge of sensible things?

            12. According to Aquinas’s discussion of the voluntariness of God’s activity (CT 96), what are the main features of God’s will?

            13. According to Aquinas’s discussion of human will (SCG 2.48, CT 129), what are the main features of human free will?

            14. According to Aquinas’s discussion of God’s governance (CT 130-1) what are the main features of secondary causes?

            15. According to Aquinas, what are solutions to the objections concerning God’s particular providence (CT 133)?

            16. According to Aquinas, what are the main features of miracles and fortuitous events (CT 136-6)?

            17. According to Aquinas, what are the main features of eternal, natural, human and divine law respectively (ST

            18. According to Aquinas’s discussion of “whether the natural law contains several principles, or only one” (ST, what is the first principle of natural law, and what are the other natural laws that follow from our inclinations?

            19. According to Aquinas’s discussion of “whether the natural law is the same in all people” (ST, what are the three levels of principles of natural law regarding their rightness and our knowledge of them?

            20. According to Aquinas’s discussion of “whether the natural law can be changed” (ST, how does he answer this regarding the second way of making changes to natural law (that is, by subtraction)?


Questions for Analysis

            1. Discussing the relation between faith and reason in Summa Contra Gentiles (SCG 1.3), Aquinas lays out a twofold division of divine truths where some are attainable through reason and others not. The implication there is that reason can arrive at some divine truths independently of faith. However, in is discussion of faith and reason in Summa Theologica (ST 1.1.1) Aquinas suggests that philosophy is unreliable and divine revelation is needed. Discuss his reasoning in both passages and whether they are compatible with each other.

            2. Aquinas considers an argument against God’s existence based on parsimony (ST 1.2.3 Obj2): the existence of the universe can be adequately explained from the two principles of matter and human will, and there is no need to postulate a God in addition to those. Discuss Aquinas’s reply to this objection and whether he succeeds.

            3. Selection one of Aquinas’s five ways for proving God’s existence (ST 1.2.3) and discuss whether it succeeds.

            4. Aquinas’s arguments for divine simplicity rest on a variety of Aristotelian metaphysical distinctions: actuality vs. potentiality, immateriality vs. materiality, intelligence vs. non-intelligence, immovability vs. movability, immutability vs. mutability, perfection vs. imperfection, simplicity vs. complexity. For Aquinas, these distinctions not only parallel each other in terms of superiority vs. inferiority, but the superior in each pair seems to imply the superior in the other pairs. Thus, complete actuality mutually implies complete immateriality, complete intelligence, complete immobility, complete immutability, complete perfection, and complete simplicity. Discuss Aquinas’s arguments for divine simplicity in CT 1.9 and ST 1.3.7 and how they rely upon these metaphysical pairs.

            5. Alvin Plantinga makes the following criticism of Aquinas's notion of divine simplicity: "if God is identical with each of his properties, then each of his properties is identical with each of his properties, so that God has but one ... This seems flatly incompatible with the obvious fact that God has several properties; he has both power and mercifulness, say, neither of which is identical with the other" (Does God have a Nature, 1980). Discuss Plantinga's objection and how Aquinas might respond.

            6. Aquinas argues that our descriptions of God are analogous to our descriptions of humans. There are two ways of making such analogies. The first is now called "analogy of proportionality" is our normal notion of analogy where “A is to B just as C is to D”. An example is “God is good just as a city mayor is good”. Each are good by exhibiting qualities that are essential for their differing job descriptions. This is not the way Aquinas uses analogy with descriptions about God. Rather, his notion of analogy is of a second type now called "analogy of attribution", and a common example is this: “If the bread is good then the baker is good”, where the baker is the cause of the bread. The baker is not warm and fluffy in the same way that the bread is, but the two are both good in their own respective ways. The goodness of the bread is thus an indication of the goodness of the baker. Similarly, we can say about God that “if the world is good, then God is good” where God is the cause of the world. The world’s goodness, then, is an indication of the creator’s goodness. Discuss Aquinas's use of analogy of attribution in CT 27 and ST 1.13.5 and whether it can result in any meaningful description about God.

            7. Aquinas agrees with Augustine that Platonic universal forms (such as, justice, chairness) exist in God's mind, which God uses as blueprints in his acts of creation. Aquinas also agrees with Augustine that humans cannot perceive the universal forms without divine illumination. However, Aquinas argues, knowledge of the world begins with sense perceptions of specific physical objects. When I look at a chair, my passive-possible intellect perceives a particular form of that particular chair. This form then gets passed on to my active-agent intellect" converts that particular form of a chair into a universal form of a chair. Aristotle had argued that the active intellect was immortal. Aquinas extends Aristotle's view and sees the active intellect as the source of divine illumination. Thus, for Aquinas, our perception of things like chairs requires both sensory experience and divine illumination. In ST 1.84.6, Aquinas presents theories of perception by Democritus, Plato and Aristotle. Discuss whether Aquinas’s theory is any better than these.

            8. In Aquinas’s discussion of “whether the natural law contains several principles, or only one” (ST, Consider the six natural inclinations that Aquinas lists, and the six corresponding principles of natural law that they imply. Are there other natural inclinations that he should have listed, and are there other ways of devising natural laws from the six that he did list?